Prostatitis in Dogs
Dr. Douglas Brum
A complete history and physical examination is the first step in obtaining an accurate diagnosis. An intact male dog with a fever, pain in the area of the prostate, and blood or pus in the urine has a high index of suspicion having acute pancreatitis. Dogs with acute prostatitis are usually quite ill and their prostate is generally painful. The diagnosis is usually more apparent in the acute condition and may require fewer diagnostics than in the chronic disease. The CBC is a useful test to run in cases of prostatitis as it evaluates the red and white blood cells. Elevations in the total white count are commonly seen in acute prostatic infections. The white blood cell count in chronic prostatitis is commonly normal, although a mild anemia may be present.
Achieving a diagnosis of chronic prostatitis is more difficult as there are less consistent clinical signs. In chronic prostatitis, it is even typical that there is no prostatic pain. The diagnostic evaluation and potential results vary significantly depending if the disease is acute or chronic.
The biochemical profile evaluates the metabolic status of a variety of organ systems. Since prostatitis is a more common occurrence on older animals, it is a useful screening test to rule out other problems and or associated disease. Liver and kidney function are evaluated. Blood sugar and electrolytes are also checked to provide a good overall assessment of the general condition of the patient. In dogs with acute prostatitis, or sepsis, hypoglycemia (a low blood sugar) and elevated liver enzymes may be present.
A urinalysis detects inflammatory changes or blood in the urine, and is generally the first test run when evaluating for prostatitis. The urine should be obtained sterilely for accurate interpretation. Animals with acute prostatitis usually show signs of infection (increased white blood cells and bacteria) in the urine. Conversely, dogs with chronic prostatitis may have a normal urinalysis, although intermittently they may present with urinary tract infections.
A culture and sensitivity of the urine helps to determine if a bacterial infection is present. A positive growth of bacteria is common with acute prostatitis. However, the results are not specific for a prostatic infection as an infection anywhere along the urinary tract (bladder, kidneys or prostate) may give positive results. Additionally, dogs with chronic prostatic infections may not have any bacterial growth on culture as the bacteria may be sequestered deep within the prostate and not be present in the urine at the time of sampling. Bacterial culture and sensitivities need to be interpreted with caution, and should be evaluated in light of the total clinical presentation of the animal.
Cytologic (microscopic) evaluation of seminal fluid is a useful diagnostic tool when testing for prostatic disease. Samples are obtained via an ejaculate and the fluid is checked for evidence of white blood cells, red blood cells and bacteria. Since the prostatic fluid is concentrated in the last part (third fraction) of the ejaculate, this is the most productive part to analyze. The sample should also be cultured. This test is not often done, in a dog with acute disease since they are generally ill, depressed, and uncomfortable, making obtaining a sample difficult. In a dog with chronic prostatitis, this is an excellent test in obtaining evidence of infection. Many times when the urine shows no evidence of infection, the prostatic fluid collected will provide the information needed to support a diagnosis of chronic disease. Samples generally show signs of bacterial infection or hemorrhage.
A prostatic massage and wash is another method for evaluating prostatic fluid. There are several techniques for obtaining this sample. Briefly, a urinary catheter is passed to the level of the prostatic urethra and the prostate is digitally massaged through the rectum. A sample is obtained by flushing fluid into the area. The fluid is then aspirated back through the catheter. This sample is submitted for cytology and culture. This technique is used most commonly chronic disease. Samples generally show signs of bacterial infection or hemorrhage.
Abdominal radiographs are useful in evaluating the abdominal organs and the extent of prostatic enlargement, but have limited use when diagnosing prostatitis. The general size and shape of the prostate is noted, and the lymph nodes that drain the prostate (sub-lumbar lymph nodes) are evaluated for enlargement. The prostate may or may not be enlarged in cases of acute or chronic prostatitis. Occasionally, in the acute disease there is a lack of contrast, or detail, in the area of the prostate.
An abdominal ultrasound can evaluate the texture and consistency of the prostate, as well as size and shape. Cysts and abscesses are easily visualized. Changes in echogenicity (texture) can be seen with any type of prostatic disease. Abdominal lymph nodes are observed for enlargement. In order to obtain a more specific diagnosis, an area that is identified as abnormal may be aspirated or biopsied using the ultrasound for guidance.
Cases of acute prostatitis usually do not require an aspirate or biopsy in order to obtain a tentative diagnosis. However, it may be very useful in chronic cases since ultrasound alone cannot differentiate chronic prostatitis from neoplasia or hyperplasia. Fine needle aspiration is less invasive than a biopsy, and may be used to collect fluid from cysts or obtain small cell samples from the prostatic tissue for cytologic evaluation (microscopic evaluation of the cells obtained). A biopsy, however, provides a better sample as a core of tissue is obtained for histopathology (microscopic examination of tissue). Biopsy usually provides more accurate information about the pathology of the prostate, since a larger amount of tissue can be evaluated.
Occasionally a clotting profile is indicated if there is significant bloody discharge from the penis or blood in the urine. Clotting tests to be considered might include an activated clotting time (ACT), a prothrombin time (PT), activated partial thromboplastin time (APTT), platelet count, and possible a von Willebrand's (VWF) test. Clotting tests are generally normal in prostatitis.